The invention relates generally to power electronics and, more particularly, to advanced cooling for power electronics.
High power converters, such as medium voltage industrial drives, frequency converters for oil and gas, traction drives, Flexible AC Transmission (FACT) devices, and other high power conversion equipment, for example rectifiers and inverters, typically include press-pack power devices with liquid cooling. Non-limiting examples of power devices include integrated gate commutated thyristors (IGCTs), diodes, insulated gate bipolar transistors (IGBTs), thyristors and gate turn-off thyristors (GTOs). Press-pack devices are particularly advantageous in high power applications, and benefits of press-packs include double-sided cooling, as well as the absence of a plasma explosion event during failure.
To construct a high power converter circuit using press-pack devices, heat sinks and press-pack devices are typically sandwiched to form a stack. State-of-the-art power converter stacks typically employ conventional liquid cooled heat sinks with larger diameter cooling channels. The heat sinks and power devices are not integrated in state of the art power converter stacks. In certain applications, thermal grease layers are disposed between respective ones of the press-pack device and the liquid cooled heat sink. In other applications, at least some of the layers are simply held together by pressure, with no thermal grease in between them. This arrangement results in significant contact resistance. Other shortcomings of such power converter stacks include relatively high thermal impedance from the semiconductor junction to the liquid, as well as a relatively complex stack assembly structure and process due to the number of parts involved.
Accordingly, it would be desirable to improve the thermal performance and packaging of power converter stacks using press-pack devices. More particularly, it would be desirable to reduce the thermal impedance from the semiconductor junction to the liquid for high reliability and/or high power density. It would further be desirable to provide a relatively simplified stack assembly structure for high maintainability.